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The upper solid layer of the lithosphere. What is the lithosphere

And any negative lithospheric changes can exacerbate the global crisis. From this article you will learn about what the lithosphere is and lithospheric plates.

Concept definition

The lithosphere is the outer hard shell of the globe, which consists of the earth's crust, part of the upper mantle, sedimentary and igneous rocks. It is rather difficult to determine its lower boundary, but it is generally accepted that the lithosphere ends with a sharp decrease in the viscosity of rocks. The lithosphere occupies the entire surface of the planet. The thickness of its layer is not the same everywhere, it depends on the terrain: on the continents - 20-200 kilometers, and under the oceans - 10-100 km.

The Earth's lithosphere mostly consists of igneous igneous rocks (about 95%). These rocks are dominated by granitoids (on the continents) and basalts (under the oceans).

Some people think that the concepts "hydrosphere" / "lithosphere" mean the same thing. But this is far from true. The hydrosphere is a kind of water shell of the globe, and the lithosphere is solid.

Geological structure of the globe

The lithosphere as a concept also includes geological structure of our planet, therefore, in order to understand what the lithosphere is, it should be considered in detail. The upper part of the geological layer is called the earth's crust, its thickness varies from 25 to 60 kilometers on the continents, and from 5 to 15 kilometers in the oceans. The lower layer is called the mantle, separated from the earth's crust by the Mohorovichich section (where the density of matter changes dramatically).

The globe is made up of the earth's crust, mantle and core. The earth's crust is a solid, but its density changes dramatically at the boundary with the mantle, that is, at the Mohorovichic line. Therefore, the density of the earth's crust is an unstable value, but the average density of a given layer of the lithosphere can be calculated, it equals 5.5223 grams / cm 3.

The globe is a dipole, that is, a magnet. Earth's magnetic poles are located in the southern and northern hemispheres.

Layers of the Earth's lithosphere

The lithosphere on the continents consists of three layers. And the answer to the question of what the lithosphere is will not be complete without considering them.

The upper layer is built from a wide variety of sedimentary rocks. The middle one is conditionally called granite, but it consists not only of granites. For example, under the oceans, the granite layer of the lithosphere is completely absent. The approximate density of the middle layer is 2.5-2.7 grams/cm 3 .

The lower layer is also conditionally called basalt. It consists of heavier rocks, its density, respectively, is greater - 3.1-3.3 grams / cm 3. The lower basalt layer is located under the oceans and continents.

The earth's crust is also classified. There are continental, oceanic and intermediate (transitional) types of the earth's crust.

The structure of lithospheric plates

The lithosphere itself is not homogeneous, it consists of peculiar blocks, which are called lithospheric plates. They include both oceanic and continental crust. Although there is a case that can be considered an exception. The Pacific lithospheric plate consists only of oceanic crust. The lithospheric blocks consist of folded metamorphic and igneous rocks.

Each continent has at its base an ancient platform, the boundaries of which are defined by mountain ranges. Plains and only individual mountain ranges are located directly on the platform area.

Seismic and volcanic activity is quite often observed at the boundaries of lithospheric plates. There are three types of lithospheric boundaries: transform, convergent, and divergent. The outlines and boundaries of lithospheric plates change quite often. Small lithospheric plates are connected to each other, while large ones, on the contrary, break apart.

List of lithospheric plates

It is customary to distinguish 13 main lithospheric plates:

Philippine plate.
Australian.
Eurasian.
Somali.
South American.
Hindustan.
African.
Antarctic Plate.
Nazca plate.
Pacific;
North American.
Scotia plate.
Arabian plate.
Cooker Coconut.

So, we gave a definition of the concept of "lithosphere", considered the geological structure of the Earth and lithospheric plates. With the help of this information, it is now possible to answer with certainty the question of what the lithosphere is.

LITHOSPHERE

Structure and composition of the lithosphere. The neomobility hypothesis. Formation of continental blocks and oceanic depressions. Movement of the lithosphere. Epeirogenesis. Orogeny. The main morphostructures of the Earth: geosynclines, platforms. Age of the Earth. Geochronology. Ages of mountain building. Geographic distribution of mountain systems of different ages.

Structure and composition of the lithosphere.

The term "lithosphere" has been used in science for a long time - probably from the middle of the 19th century. But it acquired its modern significance less than half a century ago. Even in the geological dictionary of the 1955 edition it is said: lithosphere- the same as the earth's crust. In the dictionary edition of 1973 and later: lithosphere… V modern understanding includes the earth's crust ... and rigid the upper part of the upper mantle Earth. Upper mantle is a geological term for a very large layer; the upper mantle has a thickness of up to 500, according to some classifications - over 900 km, and the lithosphere includes only the upper ones from several tens to two hundred kilometers.

The lithosphere is the outer shell of the "solid" Earth, located below the atmosphere and the hydrosphere above the asthenosphere. The thickness of the lithosphere varies from 50 km (under the oceans) to 100 km (under the continents). It consists of the earth's crust and the substrate, which is part of the upper mantle. The boundary between the earth's crust and the substratum is the Mohorovic surface, when crossing it from top to bottom, the velocity of longitudinal seismic waves increases abruptly. The spatial (horizontal) structure of the lithosphere is represented by its large blocks - the so-called. lithospheric plates separated from each other by deep tectonic faults. Lithospheric plates move in a horizontal direction at an average speed of 5-10 cm per year.

The structure and thickness of the earth's crust are not the same: that part of it, which can be called the mainland, has three layers (sedimentary, granite and basalt) and an average thickness of about 35 km. Under the oceans, its structure is simpler (two layers: sedimentary and basalt), the average thickness is about 8 km. Transitional types of the earth's crust are also distinguished (lecture 3).

In science, the opinion has firmly entrenched that the earth's crust in the form in which it exists is a derivative of the mantle. Throughout geological history, a directed irreversible process of enrichment of the Earth's surface with matter from the Earth's interior has taken place. Three main types of rocks take part in the structure of the earth's crust: igneous, sedimentary and metamorphic.

Igneous rocks are formed in the bowels of the Earth under conditions of high temperatures and pressures as a result of magma crystallization. They make up 95% of the mass of the matter that makes up the earth's crust. Depending on the conditions under which the process of magma solidification took place, intrusive (formed at a depth) and effusive (poured to the surface) rocks are formed. Intrusive ones include: granite, gabbro, igneous ones - basalt, liparite, volcanic tuff, etc.

Sedimentary rocks are formed on the earth's surface in various ways: some of them are formed from the destruction products of previously formed rocks (detrital: sands, gelatins), some due to the vital activity of organisms (organogenic: limestones, chalk, shell rock; siliceous rocks, hard and brown coal, some ores), clay (clays), chemical (rock salt, gypsum).

Metamorphic rocks are formed as a result of the transformation of rocks of a different origin (igneous, sedimentary) under the influence of various factors: high temperature and pressure in the bowels, contact with rocks of a different chemical composition, etc. (gneisses, crystalline schists, marble, etc.).

Most of the volume of the earth's crust is occupied by crystalline rocks of igneous and metamorphic origin (about 90%). However, for the geographic shell, the role of a thin and discontinuous sedimentary layer is more significant, which, on most of the earth's surface, is in direct contact with water, air, takes an active part in geographical processes (thickness - 2.2 km: from 12 km in troughs, up to 400 - 500 m in the ocean bed). The most common are clays and shale, sands and sandstones, carbonate rocks. An important role in the geographic envelope is played by loess and loess-like loams, which form the surface of the earth's crust in the non-glacial regions of the northern hemisphere.

In the earth's crust - the upper part of the lithosphere - 90 chemical elements were found, but only 8 of them are widespread and account for 97.2%. According to A.E. Fersman, they are distributed as follows: oxygen - 49%, silicon - 26, aluminum - 7.5, iron - 4.2, calcium - 3.3, sodium - 2.4, potassium - 2.4, magnesium - 2, 4%.

The earth's crust is divided into separate geologically uneven-aged, more or less active (dynamically and seismically) blocks, which are subject to constant movements, both vertical and horizontal. Large (several thousand kilometers across), relatively stable blocks of the earth's crust with low seismicity and weakly dissected relief are called platforms ( plat- flat, form- form (fr.)). They have a crystalline folded basement and a sedimentary cover of different ages. Depending on age, platforms are divided into ancient (Precambrian in age) and young (Paleozoic and Mesozoic). The ancient platforms are the cores of modern continents, the general uplift of which was accompanied by a faster rise or fall of their individual structures (shields and plates).

The substrate of the upper mantle, located on the asthenosphere, is a kind of rigid platform on which the earth's crust was formed in the course of the geological development of the Earth. The substance of the asthenosphere, apparently, is characterized by low viscosity and experiences slow displacements (currents), which, presumably, are the cause of vertical and horizontal movements of lithospheric blocks. They are in a position of isostasy, which implies their mutual balancing: the rise of some areas causes the lowering of others.

The theory of lithospheric plates was first expressed by E. Bykhanov (1877) and finally developed by the German geophysicist Alfred Wegener (1912). According to this hypothesis, before the Upper Paleozoic, the earth's crust was collected into the mainland Pangea, surrounded by the waters of the Pantallass Ocean (the Tethys Sea was part of this ocean). In the Mesozoic, splits and drift (floating) of its individual blocks (continents) began. The continents, composed of a relatively light substance, which Wegener called sial (silicium-aluminum), floated on the surface of a heavier substance, sima (silicium-magnesium). South America was the first to separate and move to the west, then Africa moved away, later Antarctica, Australia and North America. A version of the mobilism hypothesis developed later allows the existence in the past of two giant pro-continents - Laurasia and Gondwana. From the first, S. America and Asia were formed, from the second - South America, Africa, Antarctica and Australia, Arabia and Hindustan.

At first, this hypothesis (the theory of mobilism) captivated everyone, it was accepted with enthusiasm, but after 2-3 decades it turned out that the physical properties of the rocks did not allow such navigation and the theory of continental drift was put a bold cross and until the 1960s. the dominant system of views on the dynamics and development of the earth's crust was the so-called. fixism theory ( fixus- solid; unaltered; fixed (lat.), asserting the invariable (fixed) position of the continents on the surface of the Earth and the leading role of vertical movements in the development of the earth's crust.

Only by the 1960s, when the global system of mid-ocean ridges had already been discovered, a practically new theory was built, in which only a change in the relative position of the continents remained from Wegener's hypothesis, in particular, an explanation of the similarity of the outlines of the continents on both sides of the Atlantic.

The most important difference between modern plate tectonics (new global tectonics) and Wegener's hypothesis is that according to Wegener, the continents moved along the substance that composes the ocean floor, while in the modern theory, plates, which include areas of land and the ocean floor, participate in the movement; The boundaries between plates can run along the bottom of the ocean, and on land, and along the boundaries of continents and oceans.

The movement of lithospheric plates (the largest: Eurasian, Indo-Australian, Pacific, African, American, Antarctic) occurs along the asthenosphere - the layer of the upper mantle that underlies the lithosphere and has viscosity and plasticity. In places of the mid-ocean ridges, lithospheric plates are built up due to the substance rising from the bowels, and move apart along the fault axis or rifts to the sides - spreading (English spreading - expansion, distribution). But the surface of the globe cannot increase. The emergence of new sections of the earth's crust on the sides of the mid-ocean ridges must be compensated for by its disappearance somewhere. If we believe that lithospheric plates are sufficiently stable, it is natural to assume that the disappearance of the crust, as well as the formation of a new one, should occur at the boundaries of approaching plates. In this case, there can be three different cases:

Two sections of the oceanic crust are approaching;

A section of the continental crust approaches a section of the oceanic;

Two sections of the continental crust are approaching.

The process that occurs when parts of the oceanic crust approach each other can be schematically described as follows: the edge of one plate rises somewhat, forming an island arc; the other goes under it, here the level of the upper surface of the lithosphere decreases, and a deep-water oceanic trench is formed. These are the Aleutian Islands and the Aleutian Trench framing them, the Kuril Islands and the Kuril-Kamchatka Trench, the Japanese Islands and the Japanese Trench, the Mariana Islands and the Mariana Trench, etc.; all this in pacific ocean. In the Atlantic - the Antilles and the Puerto Rico Trench, the South Sandwich Islands and the South Sandwich Trench. The movement of plates relative to each other is accompanied by significant mechanical stresses, therefore, in all these places, high seismicity and intense volcanic activity are observed. The sources of earthquakes are located mainly on the surface of contact between two plates and can be at great depths. The edge of the plate, which has gone deep, plunges into the mantle, where it gradually turns into mantle matter. The submerging plate is heated, magma is melted out of it, which pours out in the volcanoes of the island arcs.

The process of submerging one plate under another is called subduction (literally, subduction). When sections of the continental and oceanic crust move towards each other, the process proceeds approximately the same as in the case of a meeting of two sections of the oceanic crust, only instead of an island arc, a powerful chain of mountains is formed along the coast of the mainland. The oceanic crust is also submerged under the continental edge of the plate, forming deep-sea trenches, volcanic and seismic processes are also intense. A typical example is the Cordillera Central and South America and a system of trenches running along the coast - Central American, Peruvian and Chilean.

When two sections of the continental crust approach each other, the edge of each of them experiences folding. Faults, mountains are formed. Seismic processes are intense. Volcanism is also observed, but less than in the first two cases, because. the earth's crust in such places is very powerful. This is how the Alpine-Himalayan mountain belt was formed, stretching from North Africa and the western tip of Europe through all of Eurasia to Indochina; it includes the most high mountains on Earth, along its entire length, high seismicity is observed, in the west of the belt there are active volcanoes.

According to the forecast, while maintaining the general direction of movement of the lithospheric plates, the Atlantic Ocean, the East African Rifts (they will be filled with the waters of the Moscow Region) and the Red Sea will expand significantly, which will directly connect the Mediterranean Sea with the Indian Ocean.

The rethinking of the ideas of A. Wegener led to the fact that, instead of the drift of the continents, the entire lithosphere began to be considered as the moving firmament of the Earth, and this theory ultimately came down to the so-called "tectonics of lithospheric plates" (today - "new global tectonics ").

The main provisions of the new global tectonics are as follows:

1. The lithosphere of the Earth, including the crust and the uppermost part of the mantle, is underlain by a more plastic, less viscous shell - the asthenosphere.

2. The lithosphere is divided into a limited number of large, several thousand kilometers across, and medium-sized (about 1000 km) relatively rigid and monolithic plates.

3. Lithospheric plates move relative to each other in a horizontal direction; The nature of these movements can be threefold:

a) spreading (spreading) with filling of the resulting gap with new oceanic-type crust;

b) underthrust (subduction) of an oceanic plate under a continental or oceanic one with the appearance of a volcanic arc or a marginal-continental volcanic-plutonic belt above the subduction zone;

c) sliding of one plate relative to another along a vertical plane, the so-called. transform faults transverse to the axes of the median ridges.

4. The movement of lithospheric plates on the surface of the asthenosphere obeys the Euler theorem, which states that the movement of conjugate points on the sphere occurs along circles drawn relative to the axis passing through the center of the Earth; the points of exit of the axis to the surface are called the poles of rotation, or disclosure.

5. On the scale of the planet as a whole, spreading is automatically compensated by subduction, i.e. how much new oceanic crust is born in a given period of time, the same amount of older oceanic crust is absorbed in subduction zones, due to which the volume of the Earth remains unchanged.

6. The movement of lithospheric plates occurs under the influence of convective currents in the mantle, including the asthenosphere. Under the axes of the separation of the median ridges, ascending currents are formed; they become horizontal at the periphery of the ridges and descend in subduction zones at the margins of the oceans. The convection itself is caused by the accumulation of heat in the bowels of the Earth due to its release during the decay of naturally radioactive elements and isotopes.

New geological materials on the presence of vertical currents (jets) of molten matter rising from the boundaries of the core and mantle itself to the earth's surface formed the basis for the construction of a new, so-called. "plume" tectonics, or plume hypotheses. It is based on the concept of internal (endogenous) energy concentrated in the lower horizons of the mantle and in the outer liquid core of the planet, the reserves of which are practically inexhaustible. High-energy jets (plumes) penetrate the mantle and rush in the form of streams into the earth's crust, thereby determining all the features of tectono-magmatic activity. Some adherents of the plume hypothesis are even inclined to believe that it is this energy exchange that underlies all physicochemical transformations and geological processes in the body of the planet.

IN Lately many researchers are increasingly inclined to believe that the uneven distribution of the Earth's endogenous energy, as well as the periodization of some exogenous processes, is controlled by external (cosmic) factors in relation to the planet. Of these, the most effective force directly affecting the geodynamic development and transformation of the Earth's matter, apparently, is the effect of the gravitational influence of the Sun, the Moon and other planets, taking into account the inertial forces of the Earth's rotation around its axis and its orbital movement. Based on this postulate concept of centrifugal planetary mills allows, firstly, to give a logical explanation of the mechanism of continental drift, and secondly, to determine the main directions of sublithospheric flows.

Movement of the lithosphere. Epeirogenesis. Orogeny.

The interaction of the earth's crust with the upper mantle is the cause of deep tectonic movements excited by the rotation of the planet, thermal convection, or gravitational differentiation of the mantle substance (slow lowering of heavier elements deep into and raising of lighter ones upwards), the zone of their appearance to a depth of about 700 km was called the tectonosphere.

There are several classifications of tectonic movements, each of which reflects one of the sides - orientation (vertical, horizontal), place of manifestation (surface, deep), etc.

From a geographical point of view, the division of tectonic movements into oscillatory (epeirogenic) and folding (orogenic) seems to be successful.

The essence of epeirogenic movements is that huge areas of the lithosphere experience slow uplifts or subsidence, are essentially vertical, deep, their manifestation is not accompanied by a sharp change in the initial occurrence of rocks. Epeirogenic movements have been everywhere and at all times in geological history. The origin of oscillatory motions is satisfactorily explained by the gravitational differentiation of matter in the Earth: ascending currents of matter correspond to uplifts of the earth's crust, and downward currents to subsidence. The speed and sign (raising - lowering) of oscillatory movements change both in space and in time. In their sequence, cyclicity is observed with intervals from many millions of years to several thousand centuries.

For the formation of modern landscapes, oscillatory movements of the recent geological past - the Neogene and the Quaternary period - were of great importance. They got the name recent or neotectonic. The range of neotectonic movements is very significant. In the Tien Shan mountains, for example, their amplitude reaches 12-15 km, and without neotectonic movements, a peneplain would exist in the place of this high mountainous country - almost a plain that arose on the site of the destroyed mountains. On the plains, the amplitude of neotectonic movements is much less, but here, too, many landforms - uplands and lowlands, the position of watersheds and river valleys - are associated with neotectonics.

The latest tectonics is also manifesting at the present time. The speed of modern tectonic movements is measured in millimeters, less often in several centimeters (in the mountains). On the Russian plain maximum speeds uplifts of up to 10 mm per year are established for the Donbass and the northeast of the Dnieper Upland, maximum subsidence, up to 11.8 mm per year, in the Pechora Lowland.

The consequences of epeirogenic movements are:

1. Redistribution of the ratio between land and sea areas (regression, transgression). The best way to study oscillatory motions is by looking at the behavior of the coastline, because in oscillatory motions the boundary between land and sea shifts due to the expansion of the sea area due to the reduction of the land area or the reduction of the sea area due to the increase in land area. If the land rises, and the sea level remains unchanged, then the sections of the seabed closest to the coastline protrude onto the day surface - occurs regression, i.e. retreat of the sea. The sinking of the land at a constant sea level, or the rise of the sea level at a stable position of the land entails transgression(advance) of the sea and the flooding of more or less significant areas of land. Thus, the main cause of transgressions and regressions is the uplift and subsidence of the solid earth's crust.

A significant increase in the area of land or sea cannot but affect the nature of the climate, which becomes more maritime or more continental, which over time should be reflected in the nature of the organic world and soil cover, the configuration of the seas and continents will change. In the event of a regression of the sea, some continents and islands may unite if the straits separating them were shallow. In transgression, on the contrary, the land masses are separated into separate continents or new islands are separated from the mainland. The presence of oscillatory movements largely explains the effect of the destructive activity of the sea. The slow transgression of the sea to the steep coasts is accompanied by the development abrasive(abrasion - cutting off the coast by the sea) of the surface and the abrasion ledge limiting it from the land side.

2. Due to the fact that the fluctuations of the earth's crust occur in different points either with a different sign, or with different intensity - the very appearance of the earth's surface is changing. Most often, uplifts or subsidences, covering vast areas, create large waves on it: during uplifts, huge domes; during subsidence, bowls and huge depressions.

During oscillatory movements, it can happen that when one section rises and the adjacent one descends, breaks occur at the boundary between such differently moving sections (and also within each of them), due to which individual blocks of the earth's crust acquire independent movement. Such a fracture, in which rocks move up or down relative to each other along a vertical or almost vertical crack, is called reset. The formation of normal faults is a consequence of crustal extension, and extension is almost always associated with uplift regions where the lithosphere swells, i.e. its profile becomes convex.

Folding movements - movements of the earth's crust, as a result of which folds are formed, i.e. of varying complexity wave-like bending of the layers. They differ from oscillatory (epeirogenic) in a number of essential features: they are episodic in time, in contrast to oscillatory ones, which never stop; they are not ubiquitous and each time confined to relatively limited areas of the earth's crust; Covering very large time intervals, however, folding movements proceed faster than oscillatory ones and are accompanied by high magmatic activity. In the processes of folding, the movement of the matter of the earth's crust always goes in two directions: horizontally and vertically, i.e. tangentially and radially. The consequence of tangential movement is the formation of folds, overthrusts, etc. The vertical movement leads to the uplift of a section of the lithosphere that is crushed into folds and to its geomorphological design in the form of a high shaft - a mountain range. Fold-forming movements are characteristic of geosynclinal areas and are poorly represented or completely absent on the platforms.

Oscillatory and folding movements are two extreme forms of a single process of the earth's crust movement. Oscillatory movements are primary, universal, at times, under certain conditions and in certain territories, they develop into orogenic movements: folding occurs in uplifting areas.

The most characteristic external expression of the complex processes of the movement of the earth's crust is the formation of mountains, mountain ranges and mountainous countries. However, in areas of different "rigidity" it proceeds differently. In areas of development of thick strata of sediments that have not yet undergone folding and, therefore, have not lost their ability to plastic deformation, folds first form, and then the entire complex folded complex is uplifted. A huge bulge of the anticlinal type arises, which subsequently, being dissected by the activity of the rivers, turns into a mountainous country.

In areas that have already undergone folding in past periods of their history, the uplift of the earth's crust and the formation of mountains occur without new folding, with the dominant development of fault dislocations. These two cases are the most characteristic and correspond to the two main types mountainous countries: the type of folded mountains (Alps, Caucasus, Cordillera, Andes) and the type of blocky mountains (Tien Shan, Altai).

Just as the mountains on Earth testify to the uplift of the earth's crust, the plains testify to subsidence. The alternation of bulges and depressions is also observed at the bottom of the ocean, therefore, it is also affected by oscillatory movements (underwater plateaus and basins indicate submerged platform structures, underwater ridges indicate flooded mountainous countries).

Geosynclinal regions and platforms form the main structural blocks of the earth's crust, which are clearly expressed in the modern relief.

The youngest structural elements of the continental crust are geosynclines. A geosyncline is a highly mobile, linearly elongated and highly dissected section of the earth's crust, characterized by multidirectional tectonic movements of high intensity, energetic phenomena of magmatism, including volcanism, and frequent and strong earthquakes. The geological structure that has arisen where the movements are geosynclinal in nature is called folded zone. Thus, it is obvious that folding is primarily characteristic of geosynclines, here it manifests itself in its most complete and vivid form. The process of geosynclinal development is complex and in many respects has not yet been sufficiently studied.

In its development, the geosyncline goes through several stages. At an early stage development in them there is a general subsidence and accumulation of thick strata of marine sedimentary and volcanic rocks. Sedimentary rocks of this stage are characterized by flyschs (a regular thin alternation of sandstones, clays, and marls), and volcanic rocks are lavas of basic composition. At the middle stage, when a thickness of sedimentary-volcanic rocks with a thickness of 8-15 km accumulates in geosynclines. The processes of subsidence are replaced by gradual uplift, sedimentary rocks undergo folding, and at great depths - metamorphization, along the cracks and ruptures penetrating them, acidic magma is introduced and solidifies. Late stage development at the site of the geosyncline under the influence of the general uplift of the surface, high folded mountains appear, crowned with active volcanoes with outpouring of lavas of medium and basic composition; depressions are filled with continental deposits, the thickness of which can reach 10 km or more. With the cessation of uplift processes, high mountains are slowly but steadily destroyed until a hilly plain is formed in their place - peneplain - with access to the surface of "geosynclinal bottoms" in the form of deeply metamorphosed crystalline rocks. Having passed the geosynclinal cycle of development, the earth's crust thickens, becomes stable and rigid, incapable of new folding. The geosyncline passes into another qualitative block of the earth's crust - platform.

Modern geosynclines on Earth are areas occupied by deep seas, classified as inland, semi-enclosed and interisland seas.

Throughout the geological history of the Earth, a number of epochs of intense folded mountain building were observed, followed by a change in the geosynclinal regime to a platform one. The most ancient of the epochs of folding belong to the Precambrian time, then follow Baikal(end of the Proterozoic - beginning of the Cambrian), Caledonian or Lower Paleozoic(Cambrian, Ordovician, Silurian, early Devonian), Hercynian or Upper Paleozoic(late Devonian, Carboniferous, Permian, Triassic), Mesozoic (Pacific), Alpine(late Mesozoic - Cenozoic).

Where seismic wave velocities decrease, indicating a change in rock plasticity. In the structure of the lithosphere, mobile areas are distinguished ( folded belts) and relatively stable platforms.

The lithosphere under oceans and continents varies considerably. The lithosphere under the continents consists of sedimentary, granite and basalt layers with a total thickness of up to 80 km. The lithosphere under the oceans has undergone many stages of partial melting as a result of the formation of oceanic crust, it is highly depleted in low-melting rare elements, mainly consists of dunites and harzburgites, its thickness is 5-10 km, and the granite layer is completely absent.

The now obsolete term was used to designate the outer shell of the lithosphere sial, derived from the name of the basic elements of rocks Si(lat. Silicium- silicon) and Al(lat. Aluminum- aluminum).

Notes

Shells of the Earth
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Synonyms:

See what "Lithosphere" is in other dictionaries:

Lithosphere ... Spelling Dictionary

- (from litho ... and Greek sphaira ball) the upper solid shell of the Earth, bounded from above by the atmosphere and hydrosphere, and from below by the asthenosphere. The thickness of the lithosphere varies within 50,200 km. Until the 60s. the lithosphere was understood as a synonym for the earth's crust. Lithosphere ... Ecological dictionary

- [σφαιρα (ρsphere) sphere] the upper solid shell of the Earth, which has great strength and passes without a definite sharp boundary into the underlying asthenosphere, the strength of which is relatively low. L. in ... ... Geological Encyclopedia

LITHOSPHERE, the upper layer of the solid surface of the Earth, which includes the CRUST and the outermost layer of the MANTLE. The lithosphere can be of different thickness from 60 to 200 km in depth. Rigid, hard and brittle, it consists of a large number tectonic plates,… … Scientific and technical encyclopedic Dictionary

- (from litho ... and sphere), the outer shell of the solid Earth, including the earth's crust and part of the upper mantle. The thickness of the lithosphere under the continents is 25,200 km, under the oceans 5,100 km. Formed mainly in the Precambrian ... Modern Encyclopedia

- (from litho ... and sphere) the outer sphere of the solid Earth, including the earth's crust and the upper part of the underlying upper mantle ... Big Encyclopedic Dictionary

Same as the earth's crust... Geological terms

The hard shell of the earth. Samoilov K.I. Marine Dictionary. M. L.: State Naval Publishing House of the NKVMF USSR, 1941 ... Marine Dictionary

Exist., number of synonyms: 1 bark (29) ASIS synonym dictionary. V.N. Trishin. 2013 ... Synonym dictionary

The upper solid shell of the Earth (50 200 km), gradually becoming less strength and density of the rock substance with the depth of the sphere. L. includes the earth's crust (up to 75 km thick on the continents and 10 km under the ocean floor) and the Earth's upper mantle ... Emergencies Dictionary

Lithosphere- Lithosphere: the solid shell of the Earth, which includes the geosphere about 70 km thick in the form of layers of sedimentary rocks (granite and basalt) and the mantle up to 3000 km thick... Source: GOST R 14.01 2005. Environmental management. General provisions And… … Official terminology

Books

Earth is a restless planet. Atmosphere, hydrosphere, lithosphere. A book for schoolchildren... and not only, L. V. Tarasov. This popular educational book opens the world of natural spheres of the Earth to the inquisitive reader - the atmosphere, hydrosphere, lithosphere. The book describes in an interesting and intelligible way…

The lithosphere is the stone shell of the Earth. From the Greek "lithos" - a stone and "sphere" - a ball

The lithosphere is the outer solid shell of the Earth, which includes the entire earth's crust with part of the Earth's upper mantle and consists of sedimentary, igneous and metamorphic rocks. The lower boundary of the lithosphere is fuzzy and is determined by a sharp decrease in rock viscosity, a change in the propagation velocity of seismic waves, and an increase in the electrical conductivity of rocks. The thickness of the lithosphere on the continents and under the oceans varies and averages 25 - 200 and 5 - 100 km, respectively.

Consider in general view geological structure of the Earth. The third planet farthest from the Sun - the Earth has a radius of 6370 km, an average density of 5.5 g / cm3 and consists of three shells - bark, robes and i. The mantle and core are divided into inner and outer parts.

The Earth's crust is a thin upper shell of the Earth, which has a thickness of 40-80 km on the continents, 5-10 km under the oceans and makes up only about 1% of the Earth's mass. Eight elements - oxygen, silicon, hydrogen, aluminum, iron, magnesium, calcium, sodium - form 99.5% of the earth's crust.

According to scientific research, scientists managed to establish that the lithosphere consists of:

Oxygen - 49%;
Silicon - 26%;
Aluminum - 7%;
Iron - 5%;
Calcium - 4%
The composition of the lithosphere includes many minerals, the most common are feldspar and quartz.

On the continents, the crust is three-layered: sedimentary rocks cover granitic rocks, and granitic rocks lie on basalt rocks. Under the oceans, the crust is "oceanic", two-layered; sedimentary rocks lie simply on basalts, there is no granite layer. There is also a transitional type of the earth's crust (island-arc zones on the outskirts of the oceans and some areas on the continents, such as the Black Sea).

The earth's crust is thickest in mountainous regions.(under the Himalayas - over 75 km), the middle one - in the areas of the platforms (under the West Siberian lowland - 35-40, within the boundaries of the Russian platform - 30-35), and the smallest - in the central regions of the oceans (5-7 km). The predominant part of the earth's surface is the plains of the continents and the ocean floor.

The continents are surrounded by a shelf - a shallow-water strip up to 200 g deep and an average width of about 80 km, which, after a sharp steep bend of the bottom, passes into the continental slope (the slope varies from 15-17 to 20-30 °). The slopes gradually level off and turn into abyssal plains (depths 3.7-6.0 km). The greatest depths (9-11 km) have oceanic trenches, the vast majority of which are located on the northern and western margins of the Pacific Ocean.

The main part of the lithosphere consists of igneous igneous rocks (95%), among which granites and granitoids predominate on the continents, and basalts in the oceans.

Blocks of the lithosphere - lithospheric plates - move along the relatively plastic asthenosphere. The section of geology on plate tectonics is devoted to the study and description of these movements.

To designate the outer shell of the lithosphere, the now obsolete term sial was used, which comes from the name of the main elements of rocks Si (lat. Silicium - silicon) and Al (lat. Aluminum - aluminum).

Lithospheric plates

It is worth noting that the largest tectonic plates are very clearly visible on the map and they are:

Pacific- the largest plate of the planet, along the boundaries of which constant collisions of tectonic plates occur and faults form - this is the reason for its constant decrease;
Eurasian- covers almost the entire territory of Eurasia (except Hindustan and the Arabian Peninsula) and contains the largest part of the continental crust;
Indo-Australian- It includes the Australian continent and the Indian subcontinent. Due to constant collisions with the Eurasian plate, it is in the process of breaking;
South American- consists of the South American mainland and part of the Atlantic Ocean;
North American- consists of the North American continent, part of northeastern Siberia, the northwestern part of the Atlantic and half of the Arctic Oceans;
African- consists of the African continent and the oceanic crust of the Atlantic and Indian Oceans. It is interesting that the plates adjacent to it move in the opposite direction from it, therefore the largest fault of our planet is located here;
Antarctic Plate- consists of the mainland Antarctica and the nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the rest of the continents are constantly moving away from it.

Movement of tectonic plates in the lithosphere

Lithospheric plates, connecting and separating, change their outlines all the time. This enables scientists to put forward the theory that about 200 million years ago the lithosphere had only Pangea - a single continent, which subsequently split into parts, which began to gradually move away from each other at a very low speed (an average of about seven centimeters per year ).

This is interesting! There is an assumption that due to the movement of the lithosphere, in 250 million years a new continent will form on our planet due to the union of moving continents.

When there is a collision of the oceanic and continental plates, the edge of the oceanic crust sinks under the continental one, while on the other side of the oceanic plate its boundary diverges from the plate adjacent to it. The boundary along which the movement of the lithospheres occurs is called the subduction zone, where the upper and plunging edges of the plate are distinguished. It is interesting that the plate, plunging into the mantle, begins to melt when the upper part of the earth's crust is squeezed, as a result of which mountains are formed, and if magma also breaks out, then volcanoes.

In places where tectonic plates come into contact with each other, there are zones of maximum volcanic and seismic activity: during the movement and collision of the lithosphere, the earth's crust collapses, and when they diverge, faults and depressions form (the lithosphere and the Earth's relief are connected to each other). This is the reason that along the edges of tectonic plates are located the most large forms relief of the Earth - mountain ranges with active volcanoes and deep-sea trenches.

Problems of the lithosphere

The intensive development of industry has led to the fact that man and the lithosphere have recently become extremely difficult to get along with each other: pollution of the lithosphere is acquiring catastrophic proportions. This happened due to the increase in industrial waste in conjunction with household waste and used in agriculture fertilizers and pesticides, which negatively affects the chemical composition of the soil and living organisms. Scientists have calculated that about one ton of garbage falls per person per year, including 50 kg of hardly decomposable waste.

Today pollution of the lithosphere has become topical issue, since nature is not able to cope with it on its own: the self-purification of the earth's crust occurs very slowly, and therefore harmful substances gradually accumulate and over time negatively affect the main culprit of the problem that has arisen - man.

Lithosphere- the outer solid shell of the Earth, which includes the entire earth's crust with part of the upper mantle of the Earth and consists of sedimentary, igneous and metamorphic rocks. The lower boundary of the lithosphere is fuzzy and is determined by a sharp decrease in rock viscosity, a change in the propagation velocity of seismic waves, and an increase in the electrical conductivity of rocks. The thickness of the lithosphere on the continents and under the oceans varies and averages 25-200 and 5-100 km, respectively.
Consider in general terms the geological structure of the Earth. The third planet farthest from the Sun - the Earth has a radius of 6370 km, an average density of 5.5 g / cm3 and consists of three shells - the crust, mantle and core. The mantle and core are divided into inner and outer parts.

solid rocks cover granite ones, and granite ones overlie basalt ones. Under the oceans, the crust is of an "oceanic", two-layer type; sedimentary rocks lie simply on basalts, there is no granite layer. There is also a transitional type of the earth's crust (island-arc zones on the margins of the oceans and some areas on the continents, such as the Black Sea). The earth's crust has the greatest thickness in mountainous regions (under the Himalayas - over 75 km), the average - in the areas of platforms (under the West Siberian lowland - 35-40, within the boundaries of the Russian platform - 30-35), and the smallest - in the central regions of the oceans (5-7 km). The predominant part of the earth's surface is the plains of the continents and the ocean floor. The continents are surrounded by a shelf - a shallow-water strip up to 200 g deep and an average width of about 80 km, which, after a sharp steep bend of the bottom, passes into the continental slope (the slope varies from 15-17 to 20-30 °). The slopes gradually level off and turn into abyssal plains (depths 3.7-6.0 km). The greatest depths (9-11 km) have oceanic trenches, the vast majority of which are located on the northern and western margins of the Pacific Ocean.

The main part of the lithosphere consists of igneous igneous rocks (95%), among which granites and granitoids predominate on the continents, and basalts in the oceans.

The relevance of the ecological study of the lithosphere due to the fact that the lithosphere is the environment of all mineral resources, one of the main objects of anthropogenic activity (component natural environment), through significant changes in which the global environmental crisis develops. In the upper part of the continental crust, soils are developed, the importance of which for humans can hardly be overestimated. Soils are an organo-mineral product of a long-term (hundreds and thousands of years) general activities living organisms, water, air, solar heat and light are among the most important natural resources. Depending on climatic and geological and geographical conditions, soils have a thickness of 15-25 cm to 2-3 m.

Soils arose together with living matter and developed under the influence of the activities of plants, animals and microorganisms until they became a very valuable fertile substrate for humans. The bulk of organisms and microorganisms of the lithosphere is concentrated in soils, at a depth of no more than a few meters. Modern soils are a three-phase system (different-grained solid particles, water and gases dissolved in water and pores), which consists of a mixture of mineral particles (rock destruction products), organic matter(waste products of the biota of its microorganisms and fungi). Soils play a huge role in the circulation of water, substances and carbon dioxide.

WITH different breeds The earth's crust, as well as its tectonic structures, are associated with various minerals: combustible, metal, construction, as well as those that are raw materials for the chemical and food industries.

Terrible ecological processes (shifts, mudflows, landslides, erosion) periodically occurred and continue to occur within the boundaries of the lithosphere, which are of great importance for the formation environmental situations in a certain region of the planet, and sometimes lead to global environmental disasters.

The deep layers of the lithosphere, which are explored by geophysical methods, have a rather complex and still insufficiently studied structure, just like the mantle and core of the Earth. But it is already known that the density of rocks increases with depth, and if on the surface it averages 2.3-2.7 g / cm3, then at a depth of close to 400 km - 3.5 g / cm3, and at a depth of 2900 km ( boundary of the mantle and the outer core) - 5.6 g/cm3. In the center of the core, where the pressure reaches 3.5 thousand tons/cm2, it increases to 13-17 g/cm3. The nature of the increase in the deep temperature of the Earth has also been established. At a depth of 100 km, it is approximately 1300 K, at a depth of close to 3000 km -4800, and in the center of the earth's core - 6900 K.

The predominant part of the Earth's matter is in a solid state, but on the border of the earth's crust and upper mantle (depths of 100-150 km) lies a stratum of softened, pasty rocks. This thickness (100-150 km) is called the asthenosphere. Geophysicists believe that other parts of the Earth may also be in a rarefied state (due to decompaction, active radio decay of rocks, etc.), in particular, the zone of the outer core. The inner core is in the metallic phase, but today there is no consensus on its material composition.

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